The present invention generally relates to the control of the amount of opening of each of a plurality of indoor expansion valves, and the rotational speed of a compressor in an air conditioner of multichamber type.
FIG. 1 is a system block diagram of a conventional multichamber air conditioner having: a compressor 1; a four-way valve 2 for switching between cooling and heating cycles; an outdoor heat exchanger 3; and outdoor expansion valve 4; an accumulator 5 provided on an outdoor machine unit 6. Each of a plurality of indoor machines 7A, 7B, and 7C is respectively provided with: indoor heat exchangers 8A, 8B, 8C; indoor expansion valves 9A, 9B, and 9C; and room temperature detectors 10A, 10B, and 10C. They are respectively disposed in the respective rooms 11A, 11B, 11C. The gas side and the liquid side of outdoor machine 6 and the respective indoor machines 7A, 7B; and 7C are respectively connected by a gas side duct 12 and a liquid side duct 13 into closed circuits. A pressure detector 14 is provided on the gas side duct 12. The system operates with a known heat pump cycle with the refrigerant being charged within the closed circuit.
The operation of the multichamber air conditioner of such a construction is described hereinafter. As shown by the solid lines of FIG. 1, during the heating operation, the refrigerant is compressed in the compressor 1 into a gas of a higher temperature and a higher pressure, and is discharged into the gas side duct 12 through the four-way valve 2, and reaches each of the indoor heat exchangers 8A, 8B, and 8C within each of the indoor machines 7A, 7B, and 7C. At such a time, each of the indoor heat exchangers 8A, 8B, and 8C functions as a condenser to heat the air of each room 11A, 11B, and 11C, so that each room 11A, 11B, and 11C is heated so as to turn the refrigerant into a condensed liquid. The pressure of the liquefied refrigerant is properly reduced in the outdoor expansion valve 4 and through each indoor expansion valve 9A, 9B, and 9C and a liquid side duct 13, and reaches the outdoor heat exchanger 3. At such a time, the outdoor heat exchanger 3 functions as an evaporator, and receives the heat from the open air so that the liquid is evaporated into a lower pressure vapor, and is sucked into the compressor 1 through the four-way valve 2, and the accumulator 5.
During the cooling operation, as shown in the broken lines of FIG. 1, the outdoor heat exchanger 3 functions as a condenser by the switching operation of the four-way valve 2. Each of the indoor heat exchangers 8A, 8B, and 8C functions as an evaporator. The respective chambers 11A, 11B, and 11C are cooled by the endothermic operation from the air of the respective rooms 11A, 11B, and 11C.
The operation of the respective indoor expansion valves 9A, 9B, and 9C is described hereinafter. When the openings of the respective indoor expansion valves 9A, 9B, and 9C increase, the amount of flow of the refrigerant increases. During the heating operation, the room temperatures of the respective rooms 11A, 11B, and 11C rise. During the cooling operation, the room temperatures are reversibly lowered. The temperatures thereof are detected by the respective room temperature detectors 10A, 10B, and 10C.
The operation of the compressor machine 1 is described hereinafter. When the rotational speed of the compressor 1 is increased, the amount of flow of the refrigerant is increased. During the heating operation, the refrigerant pressure in the gas side duct 12, which becomes a high pressure gas duct, rises. During the cooling operation, the refrigerant pressure in the gas side duct 12, which becomes a low pressure gas duct, decreases. The pressures are detected by the pressure detector 14.
In such a multichamber air conditioner, the control of the room temperature corresponds to the load of each room 11A, 11B, and 11C, and the controlling of the pressure corresponds to the total of the loads of the rooms.
FIG. 2 is a block diagram of each of the room temperature controller, and a pressure controllers of the conventional multichamber air conditioner. The respective room temperature controllers 15A, 15B, and 15C and the pressure controller 16 are so called PID controllers; the respective subtracting units 19A, 19B, 19C, and 19D are for outputting the differences among the respective outputs of the respective room temperature setting units 17A, 17B, and 17C used for setting the target values of the respective room temperatures of the respective rooms 11A, 11B, and 11C and a pressure setting unit 18 is used for setting the target value of the pressure; room temperature detectors 10A, 10B, and 10C and a pressure detector 14 are provided; integrating units 20A, 20B, 20C, and 20D are provided for integrating the respective outputs of the respective subtracting units 19A, 19B, 19C, and 19D; differentiating units 21A, 21B, 21C, 21D, 22A, 22B, 22C, and 22D are provided for differentiating the respective outputs of the respective subtracting units 19A, 19B, 19C, and 19D which are proportional coefficient setting units; elements 23A, 23B, 23C, and 23D are integral coefficient setting units; elements 24A, 24B, 24C, and 24D are differential coefficient setting units, elements 25A, 25B, 25C, and 25D are first multiplication units for outputting the products between the respective outputs of the respective subtracting units 19A, 19B, 19C, and 19D and the respective outputs of the respective proportional coefficient setting units provided 22A, 22B, 22C, and 22D; elements 26A, 26B, 26C, and 26D are second multiplication units for outputting the products between the respective outputs of the respective integrating units 20A, 20B, 20C, and 20D and the respective outputs of the respective integration coefficient setting units provided 23A, 23B, 23C, and 23D; elements 27A, 27B, 27C, and 27D are third multiplication units provided for outputting the products between the respective outputs of the differentiating units 21A, 21B, 21C, and 21D and the respective outputs of the differential coefficients setting units 24A, 24B, 24C, and 24D; adding units 28A, 28B, and 28C are for outputting the sums of the respective first multiplication units 25A, 25B, 25C, and 25C, 25D, the respective second multiplication units 26A, 26B, 26C, and 26D, and the respective third multiplication units 27A, 27B, 27C, and 21D; the amount of opening of the respective indoor expansion valves 9A, 9B, and 9C and the rotational speed of the compressor 1 are controlled by the respective outputs of the respective adding units 28A, 28B, and 28C.
The operation of the room temperature setting unit and the pressure controlling unit of such a construction 18 described hereinafter. During the cooling operation, the loads of the respective rooms 11A, 11B, and 11C are increased and the room temperatures are raised. The rise of the room temperature is detected by the respective room temperature detectors 10A, 10B, and 10C. The amount of opening of the respective indoor expansion valves 9A, 9B, and 9C are increased in the respective room temperature controlling units 15A, 15B, and 15C so as to conform to the room temperatures set by the respective room temperature setting units 17A, 17B, and 17C. The pressure changes are detected by the pressure detector 14, and the rotational speed of the compressor 1 is increased by the pressure controlling unit 16 so as to conform to the pressure established by the pressure setting unit 18. Namely, the rotational speed of the compressor 1 changes by an amount proportional to the sum of the value of the loads of the respective chambers 11A, 11B, and 11C. If the respective coefficients of the respective proportional coefficients setting units 22A, 23B, 22C, and 22D, the respective room temperature controlling units 15A, 15B, and 15C and the pressure controlling unit 16, the respective integrating coefficients setting units 23A, 23B, 23C, and 23D and the respective differential coefficients setting units 24A, 24B, 24C, and 24D are properly set in accordance with the characteristics in the output changes in the respective room temperature detectors 10A, 10B, and 10C with respect to the amount of opening changes in the respective indoor expansion valves 9A, 9B, and 9C and the output changes in the pressure detector 14 with respect to the changes of the compressor 1, then the respective outputs of the respective room temperature detectors 10A, 10B, and 10C and the pressure detector 14 conforms to the respective outputs of the respective room temperature setting units 17A, 17B, and 17C and the pressure setting unit 18 in accordance with the proper responses.
But in such a multichamber air conditioner, the amount of opening of the respective indoor expansion valves 9A, 9B, and 9C are controlled only by the outputs of the respective room temperature detectors 10A, 10B, and 10C and the rotational speed of the compressor 1 is controlled only by the output of the pressure detector 14 independently of the cycle condition within each of the indoor heat exchangers 8A, 8B, and 8C. Thus, in the variation of the room temperature set values, difference in the responses of the respective room temperatures due to the drift of the refrigerant occur, with a problem in that the responses at the partial room temperatures are delayed. Also, at the starting time, the pressure responses are delayed in the return from the initial pressure reduction because of the maldistribution of the refrigerant, with a problem that the rising time is delayed.
In such a multichamber air conditioner, the characteristics change if the operational conditions change. In a PID control system, the stability and response of the control system both change with respect to changes in operating conditions, with a problem in that the response speed has to be sacrificed so as to obtain stability. Furthermore, there is also a problem in that the response speed changes if the PID control parameters corresponding to the respective operation conditions change.
Although a table of the operation amounts corresponding to the operation conditions or the like must be set into the system in a table reference system, combination of operation conditions becomes enormous if the number of operation points increases, so that the size of the table increases so enormously that the combinations can not be really coped with.
In the control system of the compressor, a occurs phenomenon where the suction pressure is largely reduced and cannot be returned to the target value in the starting of the compressor when the drift of the refrigerant becomes large after the passage of time in the stopped condition. Namely, the suction pressure is lowered to cause a condition where the rotational speed of the compressor is reduced, with a problem in that the suction pressure can not reach the target value.